A brake system of this type is known from EP A1 0344 544. The flow control valve is arranged entirely in the brake line, that means the wheel brake connects directly to the outlet valve at least in the control phase. During pressure decrease, for instance, this has as a result that both the quantity of pressure fluid flowing through the flow control valve and the quantity of pressure fluid discharging from the wheel cylinders must be conveyed by way of the outlet valve. Therefore, the outlet valve must be dimensioned for large amounts of pressure fluid. Since large cross-sections have to be opened, and adverse effects on the control quality result.
Hence the present invention has for its object to augment the control quality in a brake system according to the type referred to hereinabove.
This object is achieved in that one of the throttles is inserted into the brake line, while the other throttle is inserted into the return line.
The flow control valve of the state of the art adjusts the quantity of pressure fluid emanating from the pump or the master cylinder, respectively, to a fixed value. It is accomplished by the present invention that both the quantity of pressure fluid emanating from the pump or the master cylinder, respectively, and the quantity of pressure fluid supplied to the wheel brake or taken therefrom in addition to each other are controlled to adopt a fixed value. Thus the inflowing quantity of pressure fluid adapts better to the respective control cycle.
A simple design of a flow control valve is obtained by providing a piston which bounds an inlet chamber with its one side and an outlet chamber with its other side. A longitudinal bore extending through the piston interconnects both chambers, the said longitudinal bore being furnished with a restrictor.
The wheel brake connects via a transverse bore and a groove at the outside of the piston to the portion of the longitudinal bore which is disposed between the restrictor and the inlet chamber.
In a preferred embodiment the restrictor is presented by two restrictors, the wheel brake connecting to the channel portion between the first and the second restrictor.
It has proven expedient to use a proportional pressure limiting valve as an outlet valve.
Hereinbelow, this idea will be explained by way of a number of embodiments, while further ideas will be described partly which can be made use of in combination with the claimed invention.